The present invention relates generally to reciprocating piston compressors for compressing fluid and more particularly to such compressors having a cantilevered suction leaf valve.
In a typical reciprocating piston compressor, a cylinder is defined by a compressor crankcase and a piston reciprocates within the cylinder to compress gaseous refrigerant therein. In a compressor to which the present invention pertains, a valve plate assembly is disposed immediate the top surface of the crankcase and a cylinder head mounted thereto. The valve plate assembly includes a suction valve operable to admit fluid into the cylinder during the suction stroke of the compressor and a discharge valve operable to exhaust fluid into a discharge space defined by the cylinder head during the discharge stroke of the compressor.
With respect to the aforementioned valve plate assembly, a valve plate covers the cylinder and includes a suction inlet port extending therethrough to provide fluid communication between the cylinder and a suction pressure chamber in the cylinder head. A cantilevered suction leaf valve also known as a "flapper" valve is mounted adjacent the cylinder facing side of the face valve plate. An unattached end of the valve is in registry with the suction inlet port of the valve plate. During the compression stroke of the compressor, the unattached end is forced by pressure to sealingly cover the suction inlet port. During the intake stroke of the compressor, the unattached end is forced away from the valve plate by fluid being drawn through the suction inlet port.
Currently, suction valves are formed of very thin metal so the flapper can flex open and closed against the valve plate.
In the past, suction leaf valves were formed by stamping out a narrow slot between the flapper portion and the surrounding structure in a piece of valve steel. The width of the slot was controlled by the tooling of the stamping machinery. A problem with the narrow slot concerns the volume of gas that can be contained within the slot between the piston and valve plate in the compressor assembly. This volume, commonly called reexpansion volume, reduces the efficiency of the compressor since the fluid within the volume is repeatedly being compressed and expanded without producing any benefit. The narrower the slot is between the leaf valve and surrounding structure the smaller the reexpansion volume.
During construction of the suction leaf valve, the leaf valve undergoes a process known as "deburring". Deburring is a process of removing the sharp metal or burrs from the edge of stamped pieces. During the deburring, the piece to be deburred is placed into a tumbler along with abrasive material. The tumbler is rotated to allow the abrasive to remove the sharp edges from the metal valve. A particular problem with these types of valves is that the tumbling media or abrasive cannot always reach into the entire narrow valve slot. This prevents the edges at the slot from being deburred.
Further, if the valve edges within the valve slot are not properly deburred, the valve life is considerably shortened.
Another potential problem is that abrasive material wedged between the valve leaf and spacer may remain there during compressor assembly. During compressor operation the abrasive material may interfere with proper valve action and reduce valve life. Also the material may become dislodged within the compressor and cause internal damage.
The present invention is directed to overcoming the aforementioned problems associated with reciprocating piston compressors having cantilevered suction leaf valves.